CodeIgniter中Cannot access offset of type string错误的Webhook求助

问题概述 #

处理Paystack支付Webhook时触发TypeError，错误信息：Cannot access offset of type string on string，错误位于PaystackWebhook.php第25行，需要提取JSON数据中data->authorization->receiver_bank_account_number字段。

错误信息 #

An uncaught Exception was encountered
Type: TypeError

Message: Cannot access offset of type string on string

Filename: /home2/usefastp/public_html/app.usefastpay.ng/application/controllers/PaystackWebhook.php

Line Number: 25

原代码 #

$data = @file_get_contents("php://input");
$event = json_decode($data, true);

$result = array_change_key_case($event, CASE_LOWER);

$e = '';
$dataarray = [];

foreach ($event as $key => $value) {
    $dataarray[$key] = $value;
    $e = addslashes($value['id'][0]);
}

接收的JSON数据 #

{
    "event": "charge.success",
    "data": {
        "id": 3589405365,
        "domain": "live",
        "status": "success",
        "reference": "000013240229232839000039349865",
        "amount": 10000,
        "message": null,
        "gateway_response": "Approved",
        "paid_at": "2024-02-29T22:29:49.000Z",
        "created_at": "2024-02-29T22:29:49.000Z",
        "channel": "dedicated_nuban",
        "currency": "NGN",
        "ip_address": null,
        "metadata": {
            "receiver_account_number": "9311879633",
            "receiver_bank": "Wema Bank",
            "custom_fields": [
                {
                    "display_name": "Receiver Account",
                    "variable_name": "receiver_account_number",
                    "value": "9311879633"
                },
                {
                    "display_name": "Receiver Bank",
                    "variable_name": "receiver_bank",
                    "value": "Wema Bank"
                }
            ]
        },
        "fees_breakdown": {
            "amount": "100",
            "formula": null,
            "type": "paystack"
        },
        "log": null,
        "fees": 100,
        "fees_split": null,
        "authorization": {
            "authorization_code": "AUTH_pxt202a52t",
            "bin": "024XXX",
            "last4": "X758",
            "exp_month": "01",
            "exp_year": "2024",
            "channel": "dedicated_nuban",
            "card_type": "transfer",
            "bank": "Guaranty Trust Bank",
            "country_code": "NG",
            "brand": "Managed Account",
            "reusable": false,
            "signature": null,
            "account_name": null,
            "sender_country": "NG",
            "sender_bank": "Guaranty Trust Bank",
            "sender_bank_account_number": "XXXXXX9758",
            "sender_name": "NOSAKHARE   ATEKHA  ENDURANCE",
            "narration": "0241459758/9311879633/ICEBERGSYNERG/N",
            "receiver_bank_account_number": "9311879633",
            "receiver_bank": "Wema Bank"
        },
        "customer": {
            "id": 160371778,
            "first_name": "Nosakhare",
            "last_name": "Nosakhare",
            "email": "zionnite@gmail.com",
            "customer_code": "CUS_kt7u83b7vi2ispc",
            "phone": "0908343",
            "metadata": {},
            "risk_action": "default",
            "international_format_phone": null
        },
        "plan": {},
        "subaccount": {},
        "split": {},
        "order_id": null,
        "paidAt": "2024-02-29T22:29:49.000Z",
        "requested_amount": 10000,
        "pos_transaction_data": null,
        "source": null
    }
}

问题原因 #

第25行$e = addslashes($value['id'][0]);存在两个核心问题：

1. foreach ($event as $key => $value)遍历的是JSON顶级键值对，第一个键是event，对应的值是字符串charge.success，此时尝试访问$value['id']相当于对字符串使用数组偏移，直接触发TypeError。
2. 原代码的遍历逻辑完全冗余，$event已经是解析后的关联数组，无需重新存入dataarray。

修复方案 #

直接解析JSON后针对性提取目标字段，同时增加合法性校验避免意外错误：

// 获取Webhook输入，移除@错误屏蔽便于排查问题
$data = file_get_contents("php://input");
if (!$data) {
    http_response_code(400);
    exit("Invalid request");
}

// 解析JSON为关联数组，校验解析结果
$event = json_decode($data, true);
if (json_last_error() !== JSON_ERROR_NONE) {
    http_response_code(400);
    exit("Invalid JSON data");
}

// 仅处理charge.success事件（可根据业务需求调整）
if ($event['event'] !== 'charge.success') {
    http_response_code(200);
    exit("Event not handled");
}

// 提取目标字段，同时检查层级是否存在
$receiverAccount = null;
if (isset($event['data']['authorization']['receiver_bank_account_number'])) {
    $receiverAccount = addslashes($event['data']['authorization']['receiver_bank_account_number']);
}

// 后续业务逻辑：如存入数据库、触发通知等
// ...

说明 #

• 移除@错误屏蔽，便于排查输入为空或JSON解析失败的问题。
• 增加JSON解析合法性校验，避免后续操作依赖无效数组。
• 直接通过数组层级访问目标字段，删除冗余遍历逻辑。
• 用isset()检查字段是否存在，防止因字段缺失触发新错误。

内容的提问来源于stack exchange，提问作者Zionnite